Scintillators are known to be used for detecting neutron radiation emitted by a radioactive source such as a nuclear reactor. Scintillators can attractively be used to monitor operational status, power levels, and fissile content in nuclear reactors in real time with relatively simple antineutrino detectors. Liquid scintillators, which are loaded with neutron absorbers, generally possess a better pulse shape discrimination (PSD) than solid scintillators, and thus, are preferred when discrimination between signals arising from neutron capture and gamma rays is required.
Especially, organic liquid scintillators are attractive since they can be produced in large quantities at low cost, they possess a high hydrogen density, and they can be doped with different neutron capture agents.
Suitable detection processes regarding electron antineutrinos generated in a nuclear power reactor involve several steps; interaction of an antineutrino with a proton producing a positron and a neutron. Subsequently, the positron interaction and annihilation and the capture of the neutron after thermalisation will yield two signals, coincident within a well-defined time window. The positron produces a scintillation signal within a few nanoseconds after the antineutrino interaction. This is a so-called prompt scintillation signal. A scintillation flash, randomly delayed up to a micro-second, appears from radiation emitted by a neutron capture agent (NCA) after neutron thermalisation. Current systems make use of gadolinium as a neutron capture agent due to the fact that it has the highest neutron capture cross section of any element. Other useful neutron capture agents include boron and lithium. It is observed that gadolinium will emit a gamma ray after neutron capture, whereas boron and lithium will emit an alpha particle. The latter provides a huge improvement in signal processing since a signal produced by an alpha particle has a different pulse shape than one produced by a gamma ray, and thus, making it easier to distinguish an alpha signal from the background, which is mainly composed of gamma rays. In this respect, it is noted that the high Q-value of the alpha decay provides a fixed and high energy to detect. The deposited energy excites the solvent or matrix used in the scintillator composition, which transfers the energy to a fluorophore, which is also present in the scintillator. The fluorophore, which absorbs the energy, will subsequently emit visible light.
The known scintillators as discussed here above can, however, be considerably improved in terms of stability of the detection system. Hence, it is the object of the present invention to provide a scintillator, which demonstrates an improved stability of the detection system.